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eth: fbnic: Handle FW mailbox completions flagged with an error

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The firmware can complete a mailbox descriptor while also setting FW_ERR
to indicate it could not process the request, for example on a mailbox
DMA error. The completion carries no valid data.

The driver did not check FW_ERR. On the Rx mailbox it would sync and
parse the stale page as a normal message, and on the Tx mailbox it
silently freed the request. If the initial capabilities exchange in
fbnic_mbx_poll_tx_ready() hit FW_ERR -- on the Tx request or on the Rx
response descriptor -- no response was parsed and the poll spun until it
timed out even though the ring was healthy.

Check FW_ERR on both mailboxes. Count it per-mailbox in
fbnic_fw_mbx.resp_error, which is also shown in debugfs, warn (rate
limited, since the bit is firmware controlled), and drop the Rx page
instead of parsing it.

In fbnic_mbx_poll_tx_ready() re-issue the capabilities request when
either the Tx or the Rx resp_error counter advances, so a FW_ERR on the
request or on its response triggers a retry rather than a timeout. A
valid capabilities response is honored before the retry check, so a
response parsed in the same poll as an unrelated FW_ERR is not discarded.
The counters are mailbox-wide rather than keyed to the capabilities
request; that is sufficient here because the exchange runs during
bring-up before any other mailbox traffic, and any spurious retry is
bounded by the existing 10s timeout.

Fixes: da3cde0820 ("eth: fbnic: Add FW communication mechanism")
Signed-off-by: Alexander Duyck <alexanderduyck@fb.com>
Reviewed-by: Simon Horman <horms@kernel.org>
Link: https://patch.msgid.link/178942023343.7700.9423398932961964439.stgit@ahduyck-xeon-server.home.arpa
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
This commit is contained in:
Alexander Duyck 2026-09-14 14:10:33 -07:00 • committed by Jakub Kicinski
commit 1b97a269a5
4 changed files with 44 additions and 3 deletions
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